There has been developed a vehicle-to-vehicle communication system. An exemplary previous vehicle-to-vehicle communication system includes a vehicle-mounted terminal for use in a vehicle, a plurality of relay stations, and a relay station management server. The relay station management server serves to receive current information about the terminal, and based on the current information about the terminal, search for which of the relay stations is available next for communication with the vehicle-mounted device. The relay station management server then calculates an estimated time for switching from one relay station to another, and forwards the calculation result to the relay station(s) concerned. (for example, Japanese laid open patent publication 2004-364006).
There is another type of vehicle-to-vehicle communication system, which is configured to include a local certificate authority, a base station, and a vehicle-mounted terminal. In such a vehicle-to-vehicle communication system, the base station distributes an area certificate to the vehicle-mounted terminal at predetermined intervals, and while receiving the area certificate being the most recent and reliable, the vehicle-mounted terminal authenticates information coming from the base station using the area certificate. (for example, Japanese laid open patent publication 2007-88737).
The concern about such a previous technology described in Japanese laid open patent publication 2004-364006 is that there is no description of how a vehicle makes an initial network entry at a high speed. Moreover, with the previous technology described in Japanese laid open patent publication 2007-88737, there is no description of how to authenticate each vehicle.